Enhanced Electrochemical Dark-Field Scattering Modulation on a Single Hybrid Core-Shell Nanostructure

We study the in situ electrochemically modulated dark-field scattering of a gold nanoparticle (AuNP) coated with the poly(3,4-ethylenedioxythiophene) (PEDOT) shell, allowing for the visualization of the oxidation reduction (redox) state of PEDOT down to a single-nanoparticle level. The presence of the gold nanoparticle as a core dramatically increases scattering cross-section, which enables the visible detection of electrochemically induced modulation, a phenomenon otherwise is not observable in dark-field microscopy of pure PEDOT nanostructures. The dynamic modulation of AuNP@PEDOT core shell nanostructures with a diameter of 100 nm is investigated for individual nanoparticles. In contrast to pure PEDOT nanoparticles with nondetectable changes, a significant 2-fold reversible increase in scattering peak intensity is revealed for the single -hybrid nanoparticle when the PEDOT shell is switched from its doped state to its dedoped state. Further in situ analysis of the core shell nanostructures with PEDOT shells at different doping states confirms that the drastic increase in scattering intensity is caused by the dramatic variation of refractive index contrast when PEDOT undergoes doping dedoping transition. Overall, fast alternation of the redox-induced dark-field scattering might provide an alternative route for real-time imaging of spatiotemporal resolved redox processes down to a single nanoparticle.